TLDR Mesotherapy with stem cells showed promising hair growth results in some patients with hair loss, but more research is needed.
This retrospective observational study evaluated the benefits and safety of mesotherapy using neonatal mesenchymal stem cells (MSC) in 40 patients with androgenetic alopecia (AGA) of grade 2 to 7. The results indicated that 70% of patients experienced a mild response, while 25% showed moderate improvement in hair growth and reduction in hair loss after four monthly treatments. One patient exhibited a 72% improvement. No major adverse events were reported, and patients were followed up for 6 months. The study concluded that while the findings were promising, larger randomized controlled studies with longer follow-ups were necessary to establish MSC therapy as a novel treatment option for AGA.
136 citations,
January 2013 in “International Journal of Trichology” 
41 citations,
September 2010 in “Journal of dermatological science” Bone marrow and umbilical cord stem cells can help grow new hair.
171 citations,
July 2007 in “Journal of Investigative Dermatology” A substance called DKK-1 increases in balding areas and causes hair cells to die when exposed to DHT.
April 2021 in “Journal of The European Academy of Dermatology and Venereology” Age, hair loss duration, menopause, and specific treatments affect hair density and caliber in female hair loss patients.
3 citations,
November 2020 in “Journal of Drugs in Dermatology” Cold plasma treatment for hair loss was well tolerated and showed improvement in most patients.
43 citations,
March 2019 in “JAMA Dermatology” Hair regrowth treatments had modest benefits for patients with long-term hair loss after chemotherapy.
January 2019 in “Acta dermatovenerologica Alpina, Pannonica et Adriatica (Tiskana izd.)” Non-ablative radio frequency can potentially increase hair count in men with androgenetic alopecia, but some may be bothered by the smell during treatment.
59 citations,
August 2018 in “The oncologist” Some breast cancer patients still experience hair loss three years after chemotherapy, especially with taxane-based treatments.